Trying to figure out what is required to be on your panel? SO was I. In an effort to clear the whole matter up (for me anyway) I made this page. I'll start out by stating the FAR. (some of the items expand, if you click on the (click to expand) thing it should open up the sub-items. Clicking it again closes them. Pretty cool, eh?

§91.205 Powered civil aircraft with standard category U.S. airworthiness certificates: Instrument and equipment requirements. 

1. General. Except as provided in paragraphs (c)(3) and (e) of this section, no person may operate a powered civil aircraft with a standard category U.S. airworthiness certificate in any operation described in paragraphs (b) through (f) of this section unless that aircraft contains the instruments and equipment specified in those paragraphs (or FAA-approved equivalents) for that type of operation, and those instruments and items of equipment are in operable condition.
2. Visual-flight rules (day). For VFR flight during the day, the following instruments and equipment are required: (click to expand)
   1. Airspeed indicator.
   2. Altimeter.
   3. Magnetic direction indicator.
   4. Tachometer for each engine.
   5. Oil pressure gauge for each engine using pressure system.
   6. Temperature gauge for each liquid-cooled engine. 
   7. Oil temperature gauge for each air-cooled engine.
   8. Manifold pressure gauge for each altitude engine.
   9. Fuel gauge indicating the quantity of fuel in each tank.
   10. Landing gear position indicator, if the aircraft has a retractable landing gear.
   11. For small civil airplanes certificated after March 11, 1996, in accordance with part 23 of this chapter, an approved aviation red or aviation white anticollision light system. In the event of failure of any light of the anticollision light system, operation of the aircraft may continue to a location where repairs or replacement can be made.
   12. If the aircraft is operated for hire over water and beyond power-off gliding distance from shore, approved flotation gear readily available to each occupant and at least one pyrotechnic signaling device. As used in this section, "shore" means that area of the land adjacent to the water which is above the high water mark and excludes land areas which are intermittently under water.
   13. An approved safety belt with an approved metal-to-metal latching device for each occupant 2 years of age or older.
   14. For small civil airplanes manufactured after July 18, 1978, an approved shoulder harness for each front seat. The shoulder harness must be designed to protect the occupant from serious head injury when the occupant experiences the ultimate inertia forces specified in §23.561(b)(2) of this chapter. Each shoulder harness installed at a flight crewmember station must permit the crewmember, when seated and with the safety belt and shoulder harness fastened, to perform all functions necessary for flight operations. For purposes of this paragraph -- (click to expand)
       1. The date of manufacture of an airplane is the date the inspection acceptance records reflect that the airplane is complete and meets the FAA-approved type design data; and
       2. A front seat is a seat located at a flight crewmember station or any seat located alongside such a seat.
   15. An emergency locator transmitter, if required by §91.207.
   16. For normal, utility, and acrobatic category airplanes with a seating configuration, excluding pilot seats, of 9 or less, manufactured after December 12, 1986, a shoulder harness for -- (click to expand)
       1. Each front seat that meets the requirements of §23.785 (g) and (h) of this chapter in effect on December 12, 1985;
       2. Each additional seat that meets the requirements of §23.785(g) of this chapter in effect on December 12, 1985.
   17. For rotorcraft manufactured after September 16, 1992, a shoulder harness for each seat that meets the requirements of §27.2 or §29.2 of this chapter in effect on September 16, 1991.
3. Visual flight rules (night). For VFR flight at night, the following instruments and equipment are required: (click to expand)
   1. Instruments and equipment specified in paragraph (b) of this section.
   2. Approved position lights.
   3. An approved aviation red or aviation white anticollision light system on all U.S.-registered civil aircraft. Anticollision light systems initially installed after August 11, 1971, on aircraft for which a type certificate was issued or applied for before August 11, 1971, must at least meet the anticollision light standards of part 23, 25, 27, or 29 of this chapter, as applicable, that were in effect on August 10, 1971, except that the color may be either aviation red or aviation white. In the event of failure of any light of the anticollision light system, operations with the aircraft may be continued to a stop where repairs or replacement can be made.
   4. If the aircraft is operated for hire, one electric landing light.
   5. An adequate source of electrical energy for all installed electrical and radio equipment.
   6. One spare set of fuses, or three spare fuses of each kind required, that are accessible to the pilot in flight.
4. Instrument flight rules. For IFR flight, the following instruments and equipment are required: (click to expand)
   1. Instruments and equipment specified in paragraph (b) of this section, and, for night flight, instruments and equipment specified in paragraph (c) of this section.
   2. Two-way radio communications system and navigational equipment appropriate to the ground facilities to be used.
   3. Gyroscopic rate-of-turn indicator, except on the following aircraft: (click to expand)
      1. Airplanes with a third attitude instrument system usable through flight attitudes of 360 degrees of pitch and roll and installed in accordance with the instrument requirements prescribed in §121.305(j) of this chapter; and
      2. Rotorcraft with a third attitude instrument system usable through flight attitudes of ±80 degrees of pitch and ±120 degrees of roll and installed in accordance with §29.1303(g) of this chapter.
   4. Slip-skid indicator.
   5. Sensitive altimeter adjustable for barometric pressure.
   6. A clock displaying hours, minutes, and seconds with a sweep-second pointer or digital presentation.
   7. Generator or alternator of adequate capacity.
   8. Gyroscopic pitch and bank indicator (artificial horizon).
   9. Gyroscopic direction indicator (directional gyro or equivalent).
5. Flight at and above 24,000 ft. MSL (FL 240). If VOR navigational equipment is required under paragraph (d)(2) of this section, no person may operate a U.S.-registered civil aircraft within the 50 states and the District of Columbia at or above FL 240 unless that aircraft is equipped with approved distance measuring equipment (DME). When DME required by this paragraph fails at and above FL 240, the pilot in command of the aircraft shall notify ATC immediately, and then may continue operations at and above FL 240 to the next airport of intended landing at which repairs or replacement of the equipment can be made.
6. Category II operations. The requirements for Category II operations are the instruments and equipment specified in -- (click to expand)
   1. Paragraph (d) of this section; and
   2. Appendix A to this part.
7. Category III operations. The instruments and equipment required for Category III operations are specified in paragraph (d) of this section.
8. Exclusions. Paragraphs (f) and (g) of this section do not apply to operations conducted by a holder of a certificate issued under part 121 or part 135 of this chapter.

[Doc. No. 18334, 54 FR 34292, Aug. 18, 1989, as amended by Amdt. 91-220, 55 FR 43310, Oct. 26, 1990; Amdt. 91-223, 56 FR 41052, Aug. 16, 1991; Amdt. 91-231, 57 FR 42672, Sept. 15, 1992; Amdt. 91-248, 61 FR 5171, Feb. 9, 1996; Amdt. 91-251, 61 FR 34560, July 2, 1996] 

Huh?

Breaking it down, I've come up with the following:

VFR Day Required

1. Airspeed Indicator
2. Altimeter. Evidently, this means ANY altimeter, not just the adjustable, barometric kind.
3. Magnetic Direction Indicator. Ohh, an MDI. ummm wouldn't that be a COMPASS??
4. Tachometer
5. Oil pressure gauge
6. Water temperature gauge (Water-cooled engine)
7. Oil temperature gauge (Air-cooled engine)
8. Manifold pressure gauge
9. Fuel gauge for each fuel tank
10. Landing gear position indicator (Not needed unless you install retractable landing gear on your RV)
11. Aviation anticollision lights (Red or white)
12. Floatation device (Not required unless you operate over water and for hire)
13. Safety belts
14. Shoulder harnesses
15. ELT
16. more Shoulder harnesses
17. even MORE Shoulder harnesses

Although not specifically stated in 91.205, you also have to have a Mode-C transponder (per 91.215) if you want fly in the National Aerospace System.

VFR Night Additional Required

1. Everything for VFR Day
2. Position lights
3. Anticollision light
4. Landing light
5. Adequate source of electricity for everything
6. Spare fuses

IFR Required

1. Everything so far
2. Two-way radio communication and navigation 
3. Gyroscopic rate-of-turn indicator
4. Slip-skip indicator
5. Adjustable Altimeter
6. Clock
7. Adequate electricity from alternator
8. Artificial Horizon
9. Directional Gyro

OK, OK, What about MY plane?

Assuming that you will have an alternator that is capable for generating adequate power. and you have a complete set of spare fuses for everything, here's what an RV builder should be concerned with:

• Airspeed indicator that works off of the pitot tube and static ports
• Adjustable Barometric Altimeter connected to the static port
• Compass
• Tachometer connected to EACH engine. (one will suffice)
• Oil Pressure gauge.
• Water temperature gauge for all of the water-cooled among us. 
• Oil temperature gauge for the air-cooled (although, I would have one even with a water-cooled engine)
• Manifold pressure gauge for each Altitude Engine. (I found out from a few people, thanks Mel and Rob!, that an Altitude engine is one that is supercharged or turbocharged. That explains why I couldn't find the Manifold Pressure gauge on the C-150 that I rent!)
• Fuel gauge for each tank
• Anticollision light suitable for night operations. Safety belts with shoulder harnesses.
• ELT. 

Additionally, then to operate VFR at night:

• Position lights
• Landing light. - for hire only (Note that this must be an Electric landing light, so no candles.)

Now, for IFR:

• A two-way comm radio
• A VOR Nav radio with CDI
• Gyroscopic turn-coordinator
• Clock with second-hand (or digital)
• Artificial horizon
• Directional Gyroscope.

That's it for the regs, now here's what I want to have additionally:

• Mode-C transponder
• Another comm radio
• Another NAV radio with localizer
• Audio panel
• Marker beacons
• DME 
• 2-axis Autopilot
• GPS
• maybe Maybe MAYBE an ADF
• Strobes
• Taxi Light
• Landing Light
• EGT
• CHT
• Fuel Flow

Rearranging it a little:

Tachometer 

VFR Day

Oil Pressure

VFR Day

Oil Temperature

VFR Day - Air Cooled Engine

Water Temperature

VFR Day - Water Cooled Engine

Manifold pressure

VFR Day - Turbocharged or Supercharged engine.

Exhaust Gas Temperature 

Not Required

Cylinder Head Temperature

Not Required

Two Fuel Gauges

VFR Day

Fuel Flow

Not required

Airspeed Indicator

VFR Day

Artificial Horizon

IFR

Altimeter

VFR Day

Turn Coordinator

IFR

Directional Gyro

IFR

Vertical Speed Indicator 

Not required

Mode-C transponder

Required by 91.215

Compass

VFR Day

Comm Radio #1

IFR

Comm Radio #2

Not required

Nav Radio #1 with Localizer 

Localizer N/R, Nav Radio IFR

Nav Radio #2

Not required

DME 

IFR - if flying above 24,000 MSL

Clock 

IFR

Marker Beacon Indicator

Not required

2-axis Autopilot

Not required

GPS

Not required

ADF

Not required

Anticollision Lights.

VFR Day

Position Lights

VFR Night

Taxi Light

Not required

Landing Light

VFR Night - for hire

Strobes

Not required

Audio Panel

Not required

Safety Belts, Harnesses

VFR

Flap position indicator 

Not required

G-Force meter

Not required

Throttle

Not required unless you want the airplane to move

Carburetor Heat

Not required unless you have a carburetor and want the engine to keep running

ok, now I'm just getting silly

For problems or questions regarding this web contact bill at kane-king.com. Be sure to remove the word "at" and replace it with the @ sign. 
Last updated: November 18, 2003.